Field
The present invention relates to a method and apparatus for forming a three-dimensional image, and more particularly, to a method and apparatus for forming a three-dimensional image by selectively expanding a thermally expandable sheet.
Background
A thermally expandable sheet (or a thermally foamable sheet) where a thermally expandable layer (or a foamable layer) containing foamable microcapsules expanding due to heating is formed on one surface of a base sheet has been known in the past. When the thermally expandable sheet is irradiated with light including infrared light after an image pattern having a high light absorption property is printed on this thermally expandable sheet, the region of the thermally expandable layer corresponding to the image pattern is selectively heated and expanded. Accordingly, it is possible to form a three-dimensional image, which corresponds to the image pattern, on one surface of the base sheet.
As the technique for forming a three-dimensional image, for example, JP-A-64-28660 discloses a method including forming a print image using black toner or ink having a high light absorption property on the surface of a thermally expandable sheet that corresponds to a thermally expandable layer, or on the back of the thermally expandable sheet that corresponds to a base sheet; and forming a three-dimensional image by heating and expanding (foaming) the microcapsules of the region of the thermally expandable layer corresponding to the print image by irradiating the thermally expandable sheet with light from a halogen lamp or the like so that light is absorbed in the print image and heat is generated.
Further, for example, JP-A-2001-150812 discloses a method including forming a color image or the like on the surface of the thermally expandable sheet that corresponds to a thermally expandable layer; forming a light absorption pattern, which is formed of a grayscale image so as to correspond to the pattern of the color image formed on the surface, on the back of the thermally expandable sheet that corresponds to a base sheet; generating heat corresponding to the grayscale of the light absorption pattern by irradiating the thermally expandable sheet with light from the back of the thermally expandable sheet; and controlling the degree of the expansion of the thermally expandable layer to adjust the bulge height of a three-dimensional image.
According to the method disclosed in JP-A-2001-150812, it is possible to form a three-dimensional image of which an arbitrary portion is controlled to have an arbitrary bulge height (foam height) according to the pattern of the color image or the like that is formed on the surface of the thermally expandable sheet corresponding to the thermally expandable layer.
However, according to the result of the inventor's verification of these methods of forming a three-dimensional image, it is found that the bulge height of the three-dimensional image is affected by the grayscale of the color image or the like formed on the surface of the thermally expandable sheet corresponding to the thermally expandable layer in addition to the grayscale of the light absorption pattern formed on the back of the thermally expandable sheet corresponding to the base sheet. For this reason, when the density of the light absorption pattern formed on the back is set so as to correspond to the pattern or the like of the color image formed on the surface of the thermally expandable sheet and the irradiation of light is performed, the three-dimensional image exceeds an intended bulge height in some grayscales of the color image or the like. Accordingly, there is a problem in that a good three-dimensional image may not be formed. Meanwhile, the problem in the related art will also be described in detail in the detailed description to be described below.